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Author Topic: gallons per inch  (Read 2571 times)
rcbeam
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« on: September 23, 2012, 03:42:06 PM »

I think I have read this someone in a post before but can't find any reference to it now.  I have an MC8 with the factory aux fuel tank. Data plate on the fuel door says 179Gals, and to not put more than 170 gallons in tanks due to federal law.  I am trying to figure out what the 170 gallon fuel level would be in the tank and how many gallons per inch that would be. 

I have a special heavy wire that I use to 'dip' my tank so see how much fuel I have... not very accurate but all I have right now and I can't get a handle on mileage yet.  I haven't had any big trips.  I take her out ever 3-4 weeks though on a Sunday for a drive down the interstate and back... usually 60-80 miles round trip.

Anyone else been through this?

Tx,
Russell
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Russell
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luvrbus
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« Reply #1 on: September 23, 2012, 03:54:37 PM »

Post the tank size for us no way anyone could answer without dimensions of the tank use 1 gal = 231 cubic inches not very hard to come up with gals per inches then or do it in cubic feet 7.48 gal per cubic ft

good luck
« Last Edit: September 23, 2012, 03:58:56 PM by luvrbus » Logged

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« Reply #2 on: September 23, 2012, 05:30:46 PM »

 So how is anyone going to know what you have in your tank at any given moment???>>>Dan
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« Reply #3 on: September 23, 2012, 05:36:07 PM »

If you run it down to the 9 gallon level you are probably going to be stranded along side of the road somewhere. Grin  I have a 144 gal tank and the most i have ever put in at one time is 110 gallons.  I usually plan to fill up after i go 700 miles, i average just over 7 miles a gallon so that puts me right at 100 gallons or less each time i pull in for fuel.
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« Reply #4 on: September 23, 2012, 06:23:45 PM »

Our Prevost has the 205 gal tank and measures 24" high to bottom of neck. It takes 8.5gal/inch. The fuel gauge never goes above 3/4 or below 1/4 so I keep a 1/2" wood dowel handy and have found that it works pretty slick for checking MPG also just by measuring the fuel level on the stick and calculating fuel consumed. If your tank stretches from one side to the other (I have a filler neck on either side of the bus) the dimensions are probably fairly close to mine. Will
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« Reply #5 on: September 23, 2012, 06:53:12 PM »

Isn't the factory aux tank on a MCI in the front bay of the bus I don't think he is speaking of the main tank if I am not mistaken he carry's over 300 gals of useable fuel

good luck
« Last Edit: September 23, 2012, 06:56:00 PM by luvrbus » Logged

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« Reply #6 on: September 23, 2012, 07:29:42 PM »

Before filling, figure out how many inches it is at full with the "dip" wire (make sure it touches bottom and doesn't bend), and then add 50 gallons, and measure again.

Take the difference in inches, then (50/difference) is your gallons/inch.

You can do more/less than 50, of course, but too few gallons will make the calculation more error prone.
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challenger440
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« Reply #7 on: September 23, 2012, 07:33:06 PM »

Main tank on my 7 is 144 gallons. 179 with auxilary.  How they could ever measure you had more than 170 on board is beyond me.  If in doubt ask if you could drive around the block!  j m
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« Reply #8 on: September 23, 2012, 07:36:13 PM »

144 main plus 35 in the aux tank in the front bay for 179 total.  They cross feed.  The main will have a sender plate, why not add a fuel guage?
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« Reply #9 on: September 23, 2012, 07:40:37 PM »

The 8 in Mohave has a 180 tank in the front bay I thought it was a big aux tank compared to a Eagle
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« Reply #10 on: September 23, 2012, 08:14:22 PM »

Ditto what boomer said. Our 9 has the same setup. Like the extra cap but hate losing the bay space. Of course we added another 100 gal aux tank up there. So we have 279 gal cap. We hate the space hog more than we hate stopping for fuel so we are planning on removing it.


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Scott & Heather
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« Reply #11 on: September 24, 2012, 06:24:48 AM »

The fuel tanks in these vintage MCI require a bit of trickery to get your dipstick properly calibrated.

The tank is taller at the fuel door end, and then it gets shorter to pass under the utility channel.

Once the fuel level is out of the bump up, you will get consistent readings, as the aux tank is a constant shape, and as noted, the two tanks are tied together with open connections.

Beware that the fuel migrates according to the level of the coach, so nose up or down will change your readings.

I know of a small town in Quebec down in the valley, with roads very steep out of town. No doubt others like it in the hill country in other parts of the continent. An aux tank equipped coach will run out of fuel climbing out of town if the tank is getting towards the 1/4 tank, due to the fuel running back into the aux from the main, and leaving the fuel pick-up in the air. Discovered by a first line coach company back in the MC9 days, who preferred that the drivers not purchase the expensive fuel in La Belle Province... needless to say, after blaming the driver for the 3rd time... drivers were authorized to purchase a suitably small amount of fuel in order to get the tank up a bit to prevent the service delivery failure.

As for the Federal Law notation on the tanks about their capacity and their usable capacity, it was, and still is, affixed to the tanks by way of the legislation that requires that fuel tanks have some room for expansion in them. The filler neck takes care of these matters, unless you turn the coach on its side, you can't get more than the noted fuel into them. So, somewhat of a moot point.

Similar legal requirement to that "Objects appear closer" sticker on all of our auto right hand side mirror.
We know, but they legislated that it has to be printed on there.

happy coaching!
buswarrior

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« Reply #12 on: September 24, 2012, 06:38:51 AM »

Can you imagine being pulled over by DOT, they inspect the tank fuel level..and tell you, "Sir you have 9 gallons too much fuel allowed by Federal law, please drive off the road into that parking lot up there so we can handle the paperwork for your ticket" so you drive a block in first gear (scream Detroit, scream!) and into the parking lot...ask him to check the level just one more time for your sanity, so he does..."Sir, I guess I was wrong, you're right at 170 gallons, sorry to waste your time"  Roll Eyes
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Scott & Heather
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« Reply #13 on: September 24, 2012, 06:45:18 AM »

All this seems like a lot of fussing for nothing.

Just fill it up and drive.

JC
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JC
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rcbeam
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« Reply #14 on: September 24, 2012, 08:51:33 AM »

Thank you to everyone that has posted a reply so far to my question.  To respond indirectly to a few, I could just "fill it up and drive" but that does not answer my question.  As for tank dimensions I have no clue.  All I can say is I have a MC8 with the stock main and auxiliary tank.  The tanks are still hooked together.  I was just hoping that  someone had already figured how many gallons of fuel the two tanks hold per inch of fuel when measured with a dip wire at the filler of the main tank.

At this point I have no idea what my fuel mileage is and I would like to begin to get a handle on that for planning purposes.  The bus starts easily, does not smoke at all, and runs great. Having mileage in line with norms would just further indicate that the engine and drive train is in fact running properly.  Knowing somewhat what my mileage is would help in planning costs for future trips.
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Russell
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« Reply #15 on: September 24, 2012, 09:57:18 AM »

Russel; Glad to see your getting running. On my MCI 8 I usually could plan on around 6.4 mpg running 65 mph in our part of the country. The inch thing is a little of a personal thing of how you place stick in tank each time (angle -how far etc) Best way is fill it up to you see fuel in neck take a trip keep record of mileage. then refill to same place. Then if you want to build stick you can do it.  If you have a hudometer  (sp) that will record your trip distance for you. Garmin will give you distance also. Or like other suggested take a stick to station with you put  mark on it put 20 in put another mark put another 20 in  or your choice of gallons differant.   Bob
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« Reply #16 on: September 24, 2012, 10:26:59 AM »

What's the temperature of the fuel?  Smiley   Volume changes with temperature. The expansion/contraction ratio for diesel is approximately 1% for every 22oF (-6oC) change in temperature.   Figure that into your equation   (I found that figure online so I don't know if it's 100% correct, but I do know it changes)

I would just fill it up... for all I know I have 8-9 gallons of water in my tank anyway.     
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rcbeam
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« Reply #17 on: September 24, 2012, 04:54:02 PM »

Bob:  glad to hear from you.  Yes, she runs fine and most of the mechanicals are in good order now, so my plan is to drive it every 3-4 weeks.  Besides I simply enjoy driving her around.  The inside is still a shell at this point.  The past 18 months or so have been a financial challenge to say the least, so maybe next year will be better and I can begin to put the inside back together.

I quickly learned that the 'dip' process is not always accurate.  I have to dip the same way and be careful not to get the wire bent or crooked and also the results changes depending on how level the coach is.

At any rate, thanks to everyone that took the time to reply.  Happy motoring everyone.

Russell
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Russell
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buswarrior
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« Reply #18 on: September 24, 2012, 09:10:39 PM »

It is quite easy to have a reliable dipstick, for those who want one.

You need a dipstick that will remain straight when inserted into the tank, and be able to maintain its structural integrity when stored.

It has to be able to reach the bottom at whatever angle the filler neck and the bodywork will allow. Or, it has to have a stop on it to rest on the edge of the filler neck, if the bottom is unobtainable.

The angle at which measurements take place must remain constant, wedging it either up or down against the filler neck to accomplish this consistency is appropriate.

Having a second dipstick to use as your template for transferring the marking to your final good one is handy.

Start with a fairly empty tank, remember, you can add more marks to the bottom of the stick as you gain experience with your set-up. And most of our bus tanks are fairly consistent in shape in the lower regions, so you may simply add marks yourself based on your experience up higher in the tank.

Find a quiet fuel pump where you aren't holding up the world with your experiments...

Dip the tank, and make a mark on the stick where the fuel level is.

Choose a unit of measure, perhaps 10 gallon increments? Once you start marking the stick, you'll decide soon enough what number of gallons gives you the spacing you want to have.

So, put 10 gallons of fuel into the tank, and then dip and mark the stick.

Repeat until full.

Depending on the shape of the fuel tank, the distance between the 10 gallon marks will change. In an MCI 7/8/9/early 102 the last couple of marks will be further apart, as the tank is much narrower towards the top and 10 gallons will have more height, if you know what I mean.

I will echo the post already made:

Always fill the tank right to the brim, and record your fuel and mileage. Right to the brim reduces the margin for error in how the coach is sitting, or in the shut off of various pumps. Full to the brim is a fairly consistent fill, from fill to fill.

Remember, a US gallon is 231 cubic inches. So for instance, in a 2' x 5' tank, an inch of fuel is over 6 gallons. That will really screw up a typical busnut's fuel mileage calculations...

You have to wait a few seconds for the foaming to die down when filling a fairly empty tank, but if you are going to bandy about your fuel economy numbers, best to be as accurate as you can be, eh?

happy coaching!
buswarrior
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« Reply #19 on: September 25, 2012, 06:55:24 AM »

Buswarrior:  a thorough and thought out explanation as usual.  Thx for the additional info.  I will give it a try.

Russell

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Russell
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« Reply #20 on: September 25, 2012, 12:35:23 PM »

Hello:   Measure your tank.   Length x width. and height.   FIgure the tank is a rectangle and measure to where the tank starts to slope.  Take that number  say 20 inches wide by 60 inches long..   20 x 60 is 1200 now the height is 12 inches.   1200 x 12 is 14400.   OK now fuel is approximately 231 inches per gallon.so divide 1400 by 231 to get 62.33  gallons which is not exact but close enough for your needs.    SO 62 gallons divided by 12 inches of height equals 5 + gallons per inch  That it for the rectangular part.  You need to figure the rest of the tank and come to a height and a figure per inch.  You can average the value or figure  the total number depending on the inch reading of the tank.
  The mci 7 tank is rectangular with a hump in the front. I figured 6  gallons per inch and calibrated the fuel gage by dipping the sender in a column of fuel and reading the value of the tank and the gage together.  I wrote the figures down and now I know fairly accurately what the fillup will be when I pull into the station.
      update to this post:::
   I looked up the calculations for the mci 7 tank and this is what I came up with:
     66 x21 x 1 inch equals 1386  divided by 231  equals 6 gals    times 23 inches of height equals 138 gallons.. the federal stamp is 136 so the calculation is close enough... FWIW.   this does not answer the posters questions but is a method to find out the answer.   Regards   mike
   

     
    
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Mike Lutestanski   Dunnellon Florida
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« Reply #21 on: October 09, 2012, 08:39:31 PM »

what federal law is this?  I people with buses carriing well over 200 gals.
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« Reply #22 on: October 10, 2012, 04:22:11 AM »

what federal law is this?  I people with buses carriing well over 200 gals.

The "law" has nothing to do with maximum fuel allowed.  It has to do with not completely filling the fuel tank to allow for expansion.
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« Reply #23 on: October 10, 2012, 09:04:30 AM »


At this point I have no idea what my fuel mileage is and I would like to begin to get a handle on that for planning purposes.  The bus starts easily, does not smoke at all, and runs great. Having mileage in line with norms would just further indicate that the engine and drive train is in fact running properly.  Knowing somewhat what my mileage is would help in planning costs for future trips.

Knowing the quantity of fuel in the tank is not necessary to check fuel mileage. You simply need to be consistent when filling the tank. Always fill to the same level, whether you use the dip stick, or the bottom of the fill tube. Then you know exactly how much fuel you burned in a given number of miles and can easily calculate the rate of burn. With that, and knowing what your total usable capacity is (120 gallons), you then know what your maximum range is and can plan accordingly. 

If you really want to know per inch, then level your coach when the tank is nearly empty, empty the tank of all fuel using a siphon or pump, and fill the tank in increments of 10 gallons, dipping and marking your dipstick with each increment. This will be very time consuming, but will be the only reliable way to get an accurate dipstick, and it will be accurate only when the coach is level (not very often).

An alternative is to calibrate the dipstick for mileage. Fill to your known full point (e.g. the bottom of the fill neck). Run a specific number of miles (e.g. 50 miles). Dip the tank and mark the dipstick. Do this for 800 miles, dipping every 50 miles. Now you have a mileage calibrated dipstick, rather than a gallon calibrated dipstick. And isn't that really what you want to know? How many miles can I go on what's left in the tank?  Roll Eyes

Incidentally, if you fill the bottom of the fill neck, you will often find that as the fuel expands in the tank you may see dripping out of the fill cap. This is especially true if you park on the curb where the fill side is slightly down hill.



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Craig Shepard
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